The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and plasma may be used to activate chemical reactions.
NAND flash memory uses dense 3D structures in order to increase memory capacity while maintaining low cost per bit and without degrading performance. Creating the 3D structures involves depositing and etching multiple layers of different films. Etching film from the 3D structures is particularly difficult because etch byproducts such as fluorine are often trapped in the 3D structures, which leads to defects and device failures.
When integrating some semiconductor substrates such as the 3-D NAND flash memory devices, one type of film (such as silicon nitride (SiN) film) needs to be etched with very high selectivity to another type of film (such as silicon dioxide (SiO2), polysilicon, etc.). Wet etching processes such as hot phosphoric acid are typically used for selectively etching the SiN film. Hot phosphoric acid has several limitations including meeting selectivity requirements with respect to low density oxide, particle and defect control (particularly in oxide fins), slow etch rate, pattern collapse from surface tension, high cost due to expensive wet chemicals and chemical waste management.